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What are specular reflection and diffuse reflection and glare ?

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What is Specular reflection ?

Specular reflection means the reflection on some in the form of a beam of light but not scattered. In this reflection unless the eye is placed in the path of the reflected beam the viewer is unaware of the existence of light.

Diffuse reflection means the reflection of light energy in the scattered form in all direction. In this reflection the viewer can see the illuminated surface but not the light source.

What is glare ?

Glare means the brightness within the field of vision of such a character as to cause annoyance, discomfort, interference with vision or eye fatigue.

What is polar curve of a lamp ?

A polar curve is a convenient way of showing how the candle power of a lamp varies in different directions. Polar curves are used to determine the M.H.C.P.,M.S.C.P. and the actual illumination of a surface by employing the candle power in the particular direction.

Why does uniformly distributed light not come from any practical type of lamp ?

Due to its unsymmetrical shape.

How are hard and long shadows avoided ?

Hard and long shadows are avoided by(a) using large numbers of small luminaires mounted over a minimum height of 2.5 metres, (2) using wide surface sources of light by using diffusing globe over filament lamp or by using indirect lighting system.

What do you mean by brightness and its unit ?

The flux emitted per unit area of the source in a direction at right angles to the surface is known as brightness. Its unit is candles / m2 or candles / 〖cm〗2 or candles / 〖ft〗2.

What is depreciation factor ?

It is the ratio of illumination under normal condition of old installation to the illumination under ideal condition of new installation.

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